DE 10 2012 112 069 A1 discloses a category-defining vacuum pump, and an upstream sound-absorbing element made of a rubber-elastic material is installed between a bowl-shaped sound-absorbing cover and a pump housing. The air that escapes from the air outlet opening in the front side of the pump housing flows through a filter housed in the upstream sound-absorber element. The further course of the air flow goes between the sound-absorbing cover and the upstream sound absorber element until the air finally enters a circumferential gap space between the outside of the primarily cylinder-shaped pump housing and the sound-absorbing cover.
Vacuum pumps of this type are, in themselves, known and are also called vane pumps, and the vacuum pump also has a motor attached to the pump housing that initiates the rotation of the rotor with the slider elements. The sound absorber is necessary to prevent potential sound emissions when operating the vacuum pump. Vacuum pumps of the type of interest here are used to generate low pressure for the purpose of engine management or for brake force boost in a vehicle. In doing so, it is desirable for the vacuum pump to operate with as little noise as possible.
It is also known that in vacuum pumps of this type, when at a standstill, the conveyed air is sucked back from the upstream chamber into the pump housing through the air outlet opening. In the process, dirt, dust, suspended particles and the like can get into the pump housing, potentially resulting in premature failure of the vacuum pump. Therefore, a filter is used in the upstream sound absorber element, and the filter prevents dirt from entering the air outlet opening when the vacuum pump is idle. A disadvantage is that the filter forms a flow resistance, and moreover, there is an effect that separated substances in the filter can be flushed out of the filter, then return to the air outlet opening and thus to the pump housing.